Historically the transportation of goods by road, rail or water involved loading individual items and was labor intensive. Cranes provided assistance for handling some loads and the advent of the fork lift truck led to the introduction of palletized loads which avoided handling of individual items when transferring between different types of transport at freight terminals. Palletized loads still offered limitations in relation to the speed of handling and especially in relation to their stacking capacity. This has led to development and widespread adoption of containers. Various sizes have now become standardized 20' (6 m) long containers are the most common. The width has become standardized at 2438 mm. Containers can be loaded at source and are easily transferred between different types of transport e.g. road, rail or ship. Forklift trucks can be used to load a container with palletized loads. Pallets are approximately 48".times.40" (1200-1000 mm) square. Ten pallet places can be accommodated in a standard container. Large ocean going vessels have been designed for handling the containers which can be stacked one on top of the other perhaps as many as seven high. Containers have the advantage of offering protection to the contents within.
There is a constant flow of containers around the globe to meet the requirements for the supply of raw materials and products. To maximise container utilization it is desirable to be able to fill a container whenever it is moved from one location to another, but it has been calculated that 20% of containers are transported empty on re-positioning runs.
Some products are still transported as bulk loads. One of the products which is still most frequently transported as a bulk load on board ship is steel coil. These coils range in weight between 7,000 kg and 25,000 kg. The coils are stored in dockside warehouses which have a large capacity say of the order of 20,000,000 to 50,000,000 kg. The capacity has to be large enough to cover the required demand for steel coils between shipments. If a more regular supply chain could be established the need for these warehouses could be reduced.
The transportation of cargoes such as steel coils as bulk cargo exposes the coils to potential damage be it mechanical damage or that resulting from exposure to sea water. Often the base material is provided with a high value coating such as an organic paint finish which needs to be protected against damage. For bulk cargo this has led to the encapsulation of the coils. Because containers can be sealed against water ingress, the need for additional protective packaging could be avoided if the coils were transported in containers and it would be particularly advantageous if it was possible to use containers which would otherwise be empty.
There are frequent container shipments and the ability to utilize containers for shipment of cargoes such as of steel coils would provide a possible solution to the above mentioned problems. However, there is a problem with the utilization of the existing construction of containers for the shipment of small high weight loads because, whilst the containers are designed to carry up to 30,000 kg, the weight has to be evenly distributed over the floor. A typical design of pallet comprises 3 or 4 longitudinal wooden bearers interconnected by a number of longitudinally spaced laterally extending planks providing a load surface for the pallet. Placing a coil of steel, say a 7,000 kg coil of steel, on a pallet of this design, say with its axis vertical for stability reasons, would impart localized loading on the container floor which would exceed its design capacity when supplemented by the dynamic loads imposed during transportation at sea.
In theory a container could carry 3.times.7,000 kg coils, 2.times.13,000 kg coils or one 25,000 kg coil. In addition to the above mentioned weight distribution problem, there is a further problem of how to load such heavy weights into a container. Various designs of fork lift truck have the capacity to lift palletized loads of 7,000 kg, 13,000 and even 25,000 kg, but they can only deposit the load into the rear of the container. Open frame containers have been developed which permit side loading, or loading by way of a crane, but there are relatively few of these containers in circulation.
In order to improve container utilization a system needs to be developed which facilitates the transportation of such large weights.
Another problem which has detracted from the utilization of containers for transportation of such large weights is the need to ensure secure stowage of cargoes such as steel coils within the container. Such large weights could easily burst their way through the container sides and the traditional approach to securing loads is to brace the load within the container, typically using wood. The construction of wooden bracing is time consuming and its subsequent disposal and/or recycling further adds to the cost. The EEC Directive on Packaging and Packaging Waste 94/62 EEC will have far reaching effects on the costs of producing and transporting of goods which requires considerable packaging. The above factors have conspired to render the bulk transportation of steel coils the most appropriate means of transportation of such items until now.